So, how does Star San turn into a yeast nutrient?

Is there any official explanation for how Star San goes from being a product that kills wild bacteria and yeast cells to becoming a helpful yeast nutrient in the wort?

I've done a few vague Google searches, without much luck.

It's all about the concentration. At the prescribed dose, it destroys bacteria cell walls. At dilute concentrations, it mostly dissociates, freeing phosphate for yeast to use. Yeast nutrient that you buy in the store is primarily nitrogen compounds and phosphates- the breakdown products of StarSan are phosphate.

dwarven_stout said:

It's all about the concentration. At the prescribed dose, it destroys bacteria cell walls. At dilute concentrations, it mostly dissociates, freeing phosphate for yeast to use. Yeast nutrient that you buy in the store is primarily nitrogen compounds and phosphates- the breakdown products of StarSan are phosphate.

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+1 only edit "concentration, dose, (&) dilute concentration" with pH.

It's all about the pH of the solution, which isn't saying DS was wrong. At pH 3 or higher Star San is an effective sanitizer. As the pH drifts/blends toward neutral (with the wort pH) it becomes nutrient.

Meh. In the end pH is just a measure of H+ concentration. I'll stick by what I said.

GilaMinumBeer said:

+1 only edit "concentration, dose, (&) dilute concentration" with pH.

It's all about the pH of the solution, which isn't saying DS was wrong. At pH 3 or higher Star San is an effective sanitizer. As the pH drifts/blends toward neutral (with the wort pH) it becomes nutrient.

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You mean pH 3 or lower, dingbat!!!1

Which isn't saying you were wrong. Or wait, yeah, it kind of does...

Just throwing this out there, the dude who made star san says a pH of 3.5 or lower and it kills ****.

HHP said:

Just throwing this out there, the dude who made star san says a pH of 3.5 or lower and it kills ****.

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Yes. I suspect that the "dude" (Charlie Talley at Five Star) would be really easy to contact for anyone who requires further clarification on this subject.

This podcast has been posted every time this question comes up, it's all over the place on here, in fact a transcript of it is even stickied at the top of the equipment/sanitiation section of the forum.

March 29, 2007 - Sanitizing with Bleach and Star San
Charlie Talley from Five Star Chemicals tells us best practices in using household bleach and Star San in sanitizing equipment.

http://media.libsyn.com/media/basicbrewing/bbr03-29-07.mp3

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Revvy said:

This podcast has been posted every time this question comes up, it's all over the place on here, in fact a transcript of it is even stickied at the top of the equipment/sanitiation section of the forum.

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Yes- and the part about bleach is worth a listen, even though I don't go near it for brewing. On brewday, it's Star San all the way.

Acidified bleach is very useful for cleaning/sanitizing things as a cheap expedient. As always, watch your clothes when mixing bleach soluitons. Bleach by itself is a poor sanitizer. Charlie Talley discusses how putting a tablespoon or so of white vinegar into the bleach & water solution makes an effective sanitizing agent. Very useful for things like killing mold.

(NB: never, ever mix vinegar directly into bleach, or you will have the same experience as the British Army that morning in 1915 when the Germans used chlorine gas on them at Ypres....)

rico567 said:

(NB: never, ever mix vinegar directly into bleach, or you will have the same experience as the British Army that morning in 1915 when the Germans used chlorine gas on them at Ypres....)

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if you do, just pee on a rag and breathe through that! That's what the Canadians did while the french and british lines fled!

I believe charlie talley was on the Brewing network as well. He discusses this yeast nutrient thing birefly.

rico567 said:

(NB: never, ever mix vinegar directly into bleach, or you will have the same experience as the British Army that morning in 1915 when the Germans used chlorine gas on them at Ypres....)

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Never heard of that before, and quickly figuring out the actual chemical reaction, it seems more myth than reality.

Sodium hypochlorite (bleach) and acetic acid (vinegar) SHOULD react to form hypochlorous acid and sodium acetate, the former probably being responsible for the enhanced disinfectant powers.

NaClO + CH3COOH → HClO + CH3COONa
[sodium hypochlorite + acetic acid → hypochlorous acid + sodium acetate]

In fact, almost any acid would seem to simply produce its sodium salt + hypocholorous acid.

Speaking of sodium "salt" though, it often brings to mind table salt, NaCl (sodium chloride) which interestingly, despite sounding perhaps the most harmless also happens to be the main exception and why I said ALMOST any. Since it requires the chloride ion, it obviously can be produced with simple HCl, hydrochloric acid (aka muriatic acid):

NaClO + 2HCl → NaCl + H2O + Cl2
[sodium hypochlorite + hydrochloric acid → sodium chloride + water + chlorine (gas)]

So... keep the pool acidifiers and water softener regenerators away from the bleach

And for the last part of today's science class, just for the hell of it, might as well tackle another misconception: Bleach + ammonia (NH3), often said to also produce chlorine gas.

NaOCl + NH3 → NH2Cl + NaOH

Clearly, no chlorine gas. But in English...

[sodium hypochlorite + ammonia → chloramine + sodium hydroxide (lye aka caustic soda)]

But just because there's no chlorine gas doesn't make it safe. Lye is a pretty caustic substance, and in heavy enough concentrations can be pretty dangerous.

And chloramine, while a liquid at room temperature, will produce fumes if in an adequately concentrated solution which will have very similar toxic effects to chlorine gas. In the continued presence of bleach (almost a given), it will continue to react to produce a few other, similarly-acting chemicals. So, while it technically may not produce chlorine gas, it's still a very stupid thing to do.

emjay, I think you're neglecting the role of water in those formulas. Neither bleach nor ammonia comes water free in household products. Proton exchange plays an important role in all those reactions.

Needless to say, mixing bleach is a dangerous proposition. It is not to be trifled with. It can, however, lead to the evolution of elemental chlorine when mixing with acids or bases under the right conditions. The kicker is where the equilibrium lies. Mixing bleach with NH4+, the species found in aqueous solution, will in fact lead to the production of some chlorine gas, with the amount being dependent mainly upon the ratios present.

KFBass said:

if you do, just pee on a rag and breathe through that! That's what the Canadians did while the french and british lines fled!

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Huh... That explains a LOT!



I keed I keed...